steveb - 10:24 pm on Jan 17, 2007 (gmt 0)

Pages without the remotest seo are hit just like seo'ed pages so that idea goes nowhere.

Google has long had, well, call it "this domain can't rank well for this search term" for some stemmed word combinations. That could be the pre-history of the phenomenon, but it is defintely a different thing.

Now, since this has gone on so long, it's possible to have targeted a term with content on a topic that has been placed in unique, rewritten form on a series of URLs, all of which rank great immediately, and tank at the next data refresh.

Stemming, posion pill keywords especially in URL, density of poison words (a completely different thing than standard keyword density)... I don't know what is being inappropriately recognized, but I do know that all four pages on a topic I've put on a particular domain over the past many months have been penalized, while only 1% of the other pages on this domain are commonly penalized (1000+ are not).

I think there are many somewhat similar (but also extremely different) phenomenon occuring, so it is big mistake to try and categorize them the same. The bottom line is in some cases Google interprets its data badly. You can switch the data around, but this is primarily Google doing a bad job in this area.